Method of forming a conductive line and a method of forming a conductive contact adjacent to and insulated from a conductive line

ABSTRACT

This invention includes methods of forming conductive lines, and methods of forming conductive contacts adjacent conductive lines. In one implementation, a method of forming a conductive line includes forming a conductive line within an elongated trench within first insulative material over a semiconductive substrate. The conductive line is laterally spaced from opposing first insulative material sidewall surfaces of the trench. The conductive line includes a second conductive material received over a different first conductive material. The second conductive material is recessed relative to an elevationally outer surface of the first insulative material proximate the trench. A second insulative material different from the first insulative material is formed within the trench over a top surface of the conductive line and within laterally opposing spaces received between the first insulative material and the conductive line. In one implementation, a conductive contact is formed adjacent to and insulated from the conductive line.

RELATED PATENT DATA

This patent resulted from a divisional application of U.S. patentapplication Ser. No. 10/925,158, filed Aug. 23, 2004 now U.S. Pat. No.7,118,966, entitled “Methods of Forming Conductive Lines”, naming ScottA. Southwick, Alex J. Schrinsky and Terrence B. McDaniel as inventors,the disclosure of which is incorporated by reference.

TECHNICAL FIELD

This invention relates to methods of forming conductive lines, and tomethods of forming conductive contacts adjacent conductive lines.

BACKGROUND OF THE INVENTION

Integrated circuits are typically formed on a semiconductor substrate,such as a silicon wafer or other semiconductive material. In general,layers of various materials which are either semiconducting, conductingor insulating, are utilized to form the integrated circuits. By way ofexample, various materials are doped, ion implanted, deposited, etched,grown, etc. using various processes. A continuing goal in semiconductorprocessing is to reduce the size of individual electronic components,thereby enabling smaller and denser integrated circuitry.

One type of integrated circuitry comprises memory circuitry, for exampledynamic random access memory (DRAM). Such comprises an array of memorycells where individual cells include a transistor and a capacitor. Thecapacitor electrically connects with one of the source/drain regions ofthe transistor and a bit or a digit line electrically connects with theother of the source/drain regions of the transistor. DRAM circuitrymight be constructed such that the capacitors are elevationally higherwithin the substrate than the bit line (buried bit line construction),or alternately with the bit line fabricated elevationally higher oroutwardly of the capacitor (bit line-over-capacitor construction). Theinvention was principally motivated in addressing issues associated withburied bit line memory circuitry, although the invention is in no way solimited, nor is it limited to memory integrated circuitry. Rather, theinvention is limited only by the accompanying claims as literally wordedwithout interpretative or limiting reference to the specification anddrawings herein, and in accordance with the doctrine of equivalents.

SUMMARY

This invention includes methods of forming conductive lines, and methodsof forming conductive contacts adjacent conductive lines. In oneimplementation, a method of forming a conductive line includes forming aconductive line within an elongated trench within first insulativematerial over a semiconductive substrate. The conductive line islaterally spaced from opposing first insulative material sidewallsurfaces of the trench. The conductive line includes a second conductivematerial received over a different first conductive material. The secondconductive material is recessed relative to an elevationally outersurface of the first insulative material proximate the trench. A secondinsulative material different from the first insulative material isformed within the trench over a top surface of the conductive line andwithin laterally opposing spaces received between the first insulativematerial and the conductive line. In one implementation, a conductivecontact is formed adjacent to and insulated from the conductive line.Such can be formed by etching a contact opening into the firstinsulative material proximate the conductive line using an etchingchemistry which is substantially selective to the second insulativematerial. Conductor material is formed within the contact opening.

Other aspects and implementations are contemplated.

BRIEF DESCRIPTION OF THE DRAWINGS

Preferred embodiments of the invention are described below withreference to the following accompanying drawings.

FIG. 1 is a diagrammatic top plan view of a portion of a semiconductorwafer fragment in process in accordance with an aspect of the invention.

FIG. 2 is a diagrammatic sectional view taken through line 2-2 in FIG.1.

FIG. 3 is a view of the FIG. 2 substrate at a processing subsequent tothat shown by FIG. 2.

FIG. 4 is a view of the FIG. 3 substrate at a processing subsequent tothat shown by FIG. 3.

FIG. 5 is a view of the FIG. 4 substrate at a processing subsequent tothat shown by FIG. 4.

FIG. 6 is a view of the FIG. 5 substrate at a processing subsequent tothat shown by FIG. 5.

FIG. 7 is a view of the FIG. 4 substrate at an alternate processing tothat depicted by FIG. 5.

FIG. 8 is a view of the FIG. 6 substrate at a processing subsequent tothat shown by FIG. 6.

FIG. 9 is a view of the FIG. 8 substrate at a processing subsequent tothat shown by FIG. 8.

FIG. 10 is a view of the FIG. 9 substrate at a processing subsequent tothat shown by FIG. 9.

FIG. 11 is a view of the FIG. 10 substrate at a processing subsequent tothat shown by FIG. 10.

FIG. 12 is a view of the FIG. 11 substrate at a processing subsequent tothat shown by FIG. 11

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

This disclosure of the invention is submitted in furtherance of theconstitutional purposes of the U.S. Patent Laws “to promote the progressof science and useful arts” (Article 1, Section 8).

Exemplary preferred embodiments of methods of forming a conductive line,and of forming a conductive contact adjacent a conductive line, aredescribed with reference to exemplary implementations depicted by FIGS.1-12. Referring initially to FIGS. 1 and 2, a semiconductor substratefragment is indicated generally with reference numeral 10. Suchcomprises a semiconductor substrate 12, for example bulk monocrystallinesilicon, having an insulative material 14 formed thereover. In thecontext of this document, the term “semiconductor substrate” or“semiconductive substrate” is defined to mean any constructioncomprising semiconductive material, including, but not limited to, bulksemiconductive materials such as a semiconductive wafer (either alone orin assemblies comprising other materials thereon), and semiconductivematerial layers (either alone or in assemblies comprising othermaterials). The term “substrate” refers to any supporting structure,including, but not limited to, the semiconductive substrates describedabove. Accordingly, semiconductor substrate 12 might comprise aplurality of insulative, conductive and semiconductive materials,including at least one semiconductive material. By way of example only,an exemplary material is bulk monocrystalline silicon, although ofcourse, semiconductor-on-insulator and other substrates are alsocontemplated, whether existing or yet-to-be developed. Insulativematerial 14 can be considered as a first insulative material forreference purposes, and not necessarily a first-in-time insulativematerial formed over semiconductor substrate 12. First insulativematerial 14 might comprise a plurality of different insulative materialsand/or layers.

An elongated trench 16 is formed into first insulative material 14 oversemiconductor substrate 12. By way of example only, an exemplary widthrange for trench 16 is from 10 Angstroms to 100 microns, with anexemplary depth range for trench 16 being from 10 Angstroms to 200microns. Such can be formed by photolithographic patterning and etchusing any existing or yet-to-be developed methods. In oneimplementation, trench 16 can be considered as having opposing sidewallsurfaces 18 and a base surface 20. In the illustrated preferredembodiment, opposing sidewall surfaces 18 are essentially parallel andvertical, and base surface 20 extends horizontally therebetween, joiningtherewith at right angles. Sloped and other than straight sidewall andbase surfaces are also of course contemplated. An exemplary preferredfirst insulative material 14 comprises a silicon oxide doped with atleast one of phosphorus and boron, for example borophosphosilicate glass(BPSG). Other, and more than one, materials are also of coursecontemplated for first insulative material 14. In the preferredembodiment, first insulative material 14 is depicted as having anelevationally outer surface 19, and which is substantially planar atleast proximate trench 16.

Referring to FIG. 3, a first conductive material 22 is deposited to linetrench 16, and a second conductive material 24 is deposited thereover towithin trench 16 effective to fill the remaining volume thereof. Anexemplary preferred thickness range for first conductive material layer22 is from 10 Angstroms to 1000 Angstroms, while that for secondconductive material layer 24 is from 10 Angstroms to 100 microns. In oneexemplary embodiment, first conductive material 22 comprises titanium,for example in any of elemental, alloy and/or compound forms. In oneparticular preferred embodiment, first conductive material 22 comprisesa composite of at least two different conductive layers, for example anelemental titanium layer and a titanium nitride layer formed thereover,for example to the same or different thicknesses relative one another.Further exemplary composites of two different materials include aninitial titanium layer having a tungsten nitride layer formed thereover.Further by way of example only, additional examples include tungstenover titanium; tungsten over titanium nitride over titanium; tungstenover tungsten nitride over titanium nitride; tungsten over tantalumnitride; and tungsten over tungsten nitride over titanium enrichedtitanium nitride. Further by way of example only, an exemplary secondconductive material 24 comprises at least one of tungsten, conductivelydoped polysilicon, aluminum, copper, nickel and a conductive metalsilicide.

Referring to FIG. 4, first and second conductive materials 22 and 24,respectively, have been removed from outwardly of outer surface 19, andto leave conductive materials 22 and 24 within trench 16. An exemplarypreferred technique for doing so is by polishing (for examplechemical-mechanical polishing) conductive materials 22 and 24 back to atleast elevationally outer surface 19 proximate trench 16, and of coursemight include some removal of material 14 commensurate therewith andsome removal of materials 22 and 24 received within trench 16 effectiveto reduce the thickness of such trench and the material receivedtherein. However most preferably, the preferred removing or polishingaction is such to effectively stop on outer surface 19 or proximatethereto.

Such describes in the depicted and preferred embodiment, an example ofbut only one preferred method of forming at least first and seconddifferent conductive materials within a trench, wherein the firstconductive material lines the trench and the second conductive materialis received over the first conductive material. However, any method ofso forming as just stated is contemplated and whether existing oryet-to-be developed.

Referring to FIG. 5, second conductive material 24 has been removed fromtrench 16 effective to recess second conductive material 24 relative toelevationally outer surface 19 of first insulative material 14 proximatetrench 16. Preferred techniques for doing so include etching, forexample one or a combination of dry etching and wet etching. For examplewhere second conductive material 24 comprises elemental tungsten, anexemplary dry etching gas is NF₃ using an inductively coupled reactorhaving zero bias/power on the lower electrode and from 150 to 250 Wattsof power on the upper electrode. Exemplary temperature and pressureconditions include a substrate temperature at from 40° C. to 140° C.,with 70° C. being a specific example, and from 7 mTorr to 15 mTorr, with10 mTorr being a specific example. An exemplary preferred flow rate forthe NF₃ is from 5 sccm to 20 sccm, with 15 sccm being a specific examplefor a six liter volume chamber. Preferably, the removing of secondconductive material 24 is conducted substantially selectively relativeto first conductive material 22, and also substantially selectivelyrelative to first insulative material 14. In the context of thisdocument, a substantially selective etch or removal is at a rate of atleast 2:1 of one material relative to a stated another material. Theabove-described NF₃ processing, by way of example only, is substantiallyselective to remove elemental tungsten material 24 selectively relativeto BPSG material 14 and a titanium/titanium nitride composite formaterial 22, and at an etch rate of about 17 Angstroms per second. Anexemplary preferred wet etching chemistry for selectively removingsecond conductive material 24 relative to the stated materials 14 and 22includes an ammonia peroxide-comprising solution or an HF solution.

In one preferred implementation, the removal of second conductivematerial 24 recesses the second conductive material from 500 Angstromsto 300 Angstroms from elevationally outer surface 19 proximate trench16, with a recess of 1,000 Angstroms being a specific example.

Referring to FIG. 6, first conductive material 22 has been removed fromopposing sidewall surfaces 18 of trench 16 effective to form aconductive line 30 within trench 16 comprising second conductivematerial 24 received over first conductive material 22. Such removing ispreferably by etching, for example one or a combination of wet etchingand dry etching. Preferably, such etching is also ideally substantiallyselective relative to second conductive material 24, and alsosubstantially selective relative to first insulative material 14. In thedepicted and exemplary preferred embodiment, the first conductivematerial etching from the trench is effective to create slots 32 and 34which extend along opposing sidewall surfaces 18 of trench 16, with thedepicted preferred embodiment slots extending completely to base surface20 of insulative material 14 of trench 16. Slots or spaces 32, 34, ofcourse, might not extend all the way to base 20. Further in the depictedpreferred embodiment, the etching is effective to form conductive line30 to have laterally opposing substantially vertical sidewalls 31extending from first insulative material 14, and from base 20 thereof,to an elevationally outer surface 33 of second conductive material 24.

By way of example only, an exemplary preferred dry etch for a firstmaterial composite of elemental titanium and titanium nitride includesCl₂ in an inductively coupled reactor where the top electrode is poweredfrom 100 to 1000 Watts and the bottom electrode is powered from 10 to500 Watts. An exemplary preferred temperature range and specific exampleis as described above in connection with the second conductive materialetch, with an exemplary preferred pressure range being from 5 mTorr to100 mTorr, with 10 mTorr being a specific example. An exemplarypreferred flow rate for the Cl₂ is from 15 sccm to 100 sccm, with 90sccm being a specific example. Such etching conditions can selectivelyetch first conductive material 22 substantially selectively relative totungsten and BPSG. An exemplary preferred wet etching chemistry forselectively removing first conductive material 22 substantiallyselectively relative to the stated materials 14 and 24 includes hotphosphoric acid.

In one preferred embodiment, the removal of the first conductivematerial and the removal of the second conductive material is conductedin the same chamber under subatmospheric conditions without breaking thevacuum between such removals.

FIGS. 5 and 6 depict an exemplary method whereby the removal of thesecond conductive material occurs prior to removing the first conductivematerial. However, the reverse is also contemplated whereby removal ofthe first conductive material occurs prior to removal of the secondconductive material, by way of example only, as shown in FIG. 7 withrespect to a substrate fragment 10 a. Such depicts an alternateprocessing to that of FIG. 5, whereby first conductive material 22 hasbeen removed, preferably by etching, for example using the exemplaryabove chemistry for first material 22, and preferably forming thedepicted slots 32 a and 34 a. Subsequent processing would be conductedfor removing second conductive material 24 from the FIG. 7 construction,for example to result in the depicted FIG. 6 construction.

By way of example only, the above processing describes and depictsexemplary methods of forming a conductive line within an elongatedtrench within first insulative material over a semiconductive substrate.Such conductive line is laterally spaced from opposing first insulativematerial sidewall surfaces of the trench. The conductive line comprisesa second conductive material received over a different first conductivematerial, with the second conductive material being recessed relative toan elevationally outer surface of the first insulative materialproximate the trench. Any other method of so forming, whether existingor yet-to-be developed, is also contemplated with the above-describedFIGS. 1-7 embodiment constituting but one preferred implementation.

Referring to FIG. 8, a second insulative material 40, different fromfirst insulative material 14, has been deposited to within trench 16over top and side surfaces of conductive line 30, and to within trenchslots 32 and 34 in the depicted preferred embodiment. By way of exampleonly, and for example where first insulative material 14 comprises BPSG,an exemplary second insulative material 40 is silicon nitride. Suchprovides but one example of forming a second insulative material,different from the first insulative material, within the trench over atop surface of the conductive line and within laterally opposing spacesreceived between the first insulative material and the conductive line.In one preferred embodiment, for example as shown in FIG. 9, secondinsulative material 40 is removed from outwardly of first insulativematerial 14 at least to the outer surface thereof, for example by apolishing action such as chemical-mechanical polishing. Further by wayof example only in FIG. 9, first insulative material 14 and secondinsulative material 40 are formed to have planar outermost surfaces, andwhich in the depicted preferred example are co-planar.

The invention also contemplates forming a conductive contact adjacent toand isolated/insulated from a conductive line, for example as isdescribed by way of example only in connection with FIGS. 10-12. FIG. 10depicts substrate fragment 10 as comprising an etch mask 50, for examplephotoresist, multi-level resist, or one or more etch hard maskingmaterials. A mask opening 52 has been formed within etch mask 50, and inthe depicted embodiment shows some degree of misalignment resulting inmask opening 52 overlying at least a portion of second insulativematerial 40.

Referring to FIG. 11, a contact opening 55 has been etched into firstinsulative material 14 proximate conductive line 30, and in the depictedpreferred embodiment through mask opening 52, using an etching chemistrywhich is substantially selective to the removal of first insulativematerial 14 relative to second insulative material 40. Ideally, contactopening 55 would extend to some conductive or semiconductive region ormaterial either within first insulative material 14 or to some portionof substrate 12, for making electrical connection therewith. By way ofexample only where first insulative material 14 comprises BPSG andsecond insulative material 40 comprises silicon nitride, an exemplaryetching chemistry includes a combination of C₄F₆, C₄F₈, O₂ and Ar.

Referring to FIG. 12, etch mask 50 has been removed from substrate 10,and a conductor material 60 formed within contact opening 55. Such mightcomprise one or more conductive and/or semiconductive materials, forexample conductively doped polysilicon, elemental metals and conductivemetal nitrides. In the depicted preferred and exemplary embodiment,conductor material 60 within contact opening 55 contacts secondinsulative material 40.

In one preferred embodiment, the conductive line comprises a burieddigit line of DRAM circuitry, for example and by way of example only asshown in U.S. Pat. Nos. 6,376,380 and 6,337,274, which are hereinincorporated by reference.

In compliance with the statute, the invention has been described inlanguage more or less specific as to structural and methodical features.It is to be understood, however, that the invention is not limited tothe specific features shown and described, since the means hereindisclosed comprise preferred forms of putting the invention into effect.The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

1. A method of forming a conductive line, comprising: forming aconductive line within an elongated trench within first insulativematerial over a semiconductive substrate, the conductive line beingeverywhere laterally spaced from opposing first insulative materialsidewall surfaces of the trench, the conductive line comprising a secondconductive material received over a different first conductive material,the second conductive material being recessed elevationally relative toan elevationally outer surface of the first insulative materialproximate the trench; and forming a second insulative material differentfrom the first insulative material within the trench over a top surfaceof the conductive line and within laterally opposing spaces receivedbetween the first insulative material and the conductive line.
 2. Themethod of claim 1 wherein the second conductive material comprises atleast one of tungsten, conductively doped polysilicon, aluminum, copper,nickel and a conductive metal silicide.
 3. The method of claim 2 thesecond conductive material comprises elemental tungsten.
 4. The methodof claim 1 wherein the first conductive material comprises titanium. 5.The method of claim 4 wherein the first conductive material comprises acomposite of elemental titanium and titanium nitride layers.
 6. Themethod of claim 5 the second conductive material comprises elementaltungsten.
 7. The method of claim 1 wherein the first insulative materialcomprises silicon oxide doped with at least one of phosphorus and boron,and the second insulative material comprises silicon nitride.
 8. Themethod of claim 1 wherein the second conductive material is recessedfrom 500 Angstroms to 3000 Angstroms from said elevationally outersurface of the first insulative material.
 9. The method of claim 1wherein the elevationally outer surface of the first insulative materialis substantially planar at least proximate the trench, the forming ofthe second insulative material comprising depositing the secondinsulative material and polishing it back at least to said elevationallyouter surface of the first insulative material.
 10. The method of claim1 wherein the first and second insulative materials are formed to haveplanar outermost surfaces, and which are coplanar.
 11. The method ofclaim 1 wherein the conductive line comprises a buried digit line ofDRAM circuitry.
 12. A method of forming a conductive contact adjacent toand insulated from a conductive line, comprising: forming a conductiveline within an elongated trench within first insulative material over asemiconductive substrate, the conductive line being everywhere laterallyspaced from opposing first insulative material sidewall surfaces of thetrench, the conductive line comprising a second conductive materialreceived over a different first conductive material, the secondconductive material being recessed elevationally relative to anelevationally outer surface of the first insulative material proximatethe trench; forming a second insulative material different from thefirst insulative material within the trench over a top surface of theconductive line and within laterally opposing spaces received betweenthe first insulative material and the conductive line; etching a contactopening into the first insulative material proximate the conductive lineusing an etching chemistry which is substantially selective to thesecond insulative material; and forming conductor material within thecontact opening.
 13. The method of claim 12 wherein the conductormaterial contacts the second insulative material.
 14. The method ofclaim 12 wherein the etching comprises using an etch mask having a maskopening therein through which the first insulative material is etched,the mask opening overlapping the second insulative material.
 15. Themethod of claim 14 wherein the conductor material contacts the secondinsulative material.
 16. The method of claim 12 wherein the secondconductive material comprises at least one of tungsten, conductivelydoped polysilicon, aluminum, copper, nickel and a conductive metalsilicide.
 17. The method of claim 16 the second conductive materialcomprises elemental tungsten.
 18. The method of claim 12 wherein thefirst conductive material comprises titanium.
 19. The method of claim 18wherein the first conductive material comprises a composite of elementaltitanium and titanium nitride layers.
 20. The method of claim 19 thesecond conductive material comprises elemental tungsten.
 21. The methodof claim 12 wherein the first insulative material comprises siliconoxide doped with at least one of phosphorus and boron, and the secondinsulative material comprises silicon nitride.
 22. The method of claim12 wherein the second conductive material is recessed from 500 Angstromsto 3000 Angstroms from said elevationally outer surface of the firstinsulative material.
 23. The method of claim 12 wherein theelevationally outer surface of the first insulative material issubstantially planar at least proximate the trench, the forming of thesecond insulative material comprising depositing the second insulativematerial and polishing it back at least to said elevationally outersurface of the first insulative material.
 24. The method of claim 12wherein the conductive line comprises a buried digit line of DRAMcircuitry.
 25. A method of forming a conductive line, comprising:forming a conductive line within an elongated trench within firstinsulative material over a semiconductive substrate, the conductivematerial sidewall surfaces of the trench, the conductive line comprisinga second conductive material received over a different first conductivematerial, the second conductive material being recessed elevationallyrelative to an elevationally outer surface of the first insulativematerial proximate the trench; and forming a second insulative materialdifferent from the first insulative material within the trench over atop surface of the conductive line and within laterally opposing spacesreceived between the first insulative material and conductive line, theforming of the second insulative material comprising depositing thesecond insulative material and polishing it back at least to the firstinsulative material.
 26. A method of forming a conductive contactadajacent to and insulated from a conductive line, comprising: forming aconductive line within an elongated trench within first insulativematerial over a semiconductive substrate, the conductive line beingeverywhere laterally spaced from opposing first insulative materialsidewall surfaces of the trench, the conductive line comprising a secondconductive material received over a different first conductive material,the second conductive material being recessed elevationally relative toan elevationally outer surface of the first insulative materialproximate the trench; forming a second insulative material differentfrom the first insulative material within the trench over a top surfaceof the conductive line and within laterally opposing spaces receivedbetween the first insulative material and the conductive line, theforming of the second insulative material comprising depositing thesecond insulative material and polishing it back at least to the firstinsulative material; etching a contact opening into the first insulativematerial proximate the conductive line using an etching chemistry whichis substantially selective to the second insulative material; andforming conductor material within the contact opening.
 27. A method offorming a conductive contact adjacent to and insulated from a conductiveline, comprising: forming a conductive line within an elongated trenchwithin first insulative material over a semiconductive substrate, theconductive line being everywhere laterally spaced from opposing firstinsulative material sidewall surfaces of the trench, the conductive linecomprising a second conductive material received over a different firstconductive material, the second conductive material being recessedelevationally relative to an elevationally outer surface of the firstinsulative material proximate the trench; forming a second insulativematerial different from the first insulative material within the trenchover a top surface of the conductive line and within laterally opposingspaces received between the first insulative material and the conductiveline, the forming of the second insulative material comprisingdepositing the second insulative material and polishing it back at leastto the first insulative material; etching a contact opening into thefirst insulative material proximate the conductive line using an etchingchemistry which is substantially selective to the second insulativematerial, the etching exposing the second insulative material; andforming conductor material within the contact opening in contact withthe second insulative material.